In this project we have demonstrated first that Friend erythroleukemia cells can be induced for erythrodifferentiation by adding hemin to the tissue culture media. We have demonstrated that this results in an increase in globin chain synthesis and in globin mRNA content. We have also demonstrated that extracts of Friend erythroleukemia cells have a protein synthesis component which is influenced by the addition of hemin in vitro. Addition of 150 micron mol hemin to protein synthesis reactions results in a two-fold stimulation of endogenous synthesis. When extracts are treated with micrococcal nuclease to obtain an mRNA dependent translational system, 10- to 20-fold stimulation by hemin is obtained. Current work includes attempting to demonstrate the presence of an inhibitor of protein synthesis analogous to the heme controlled inhibitor in rabbit reticulocytes. We are also developing an active transcriptional system using permeabilized Friend erythroleukemia cells. We intend to use S-substituted nucleotides and DNA-RNA hybridization to quantitate initiation of globin gene transcription in Friend erythroleukemia cells.